Jupiter’s Spots Change Dramatically

A third red spot has appeared alongside the Great Red Spot and Red Spot Jr. in the turbulent Jovian atmosphere. The visible-light images were taken on May 9 and 10 with Hubble's Wide Field and Planetary Camera 2.Credit: NASA, ESA, and M. Wong and I. de Pater (University of California, Berkeley)

A potentially historic
change is occurring on Jupiter. An upstart storm now rivals the gas giant's Big
Red Spot as king of storms, astronomers announced last week.

The Little Red Spot, as it
was named upon discovery in 2006, shows both size and speed in threatening
to knock the former champion off its perch, with Junior's maximum winds
reaching 384 mph (172meters per second).

"In terms of maximum
wind speed, the Little Red Spot as measured in 2007 and the Great Red Spot
when last measured in 2000 are just about the same," said Andrew Cheng,
physicist and lead study author at Johns Hopkins University Applied Physics
Laboratory in Laurel, Maryland.

Those winds far outstrip the
156 mph threshold that defines a Category 5 hurricane on Earth, and the Little
Red Spot itself appears nearly as big as our whole planet.

Seeing spots

A third red spot on Jupiter
was also announced
last week by a different team, joining its larger super-storm cousins. The
Great Red Spot has raged on for at least two centuries and perhaps as much as
350 years, ancient observations suggest.

Cheng's team used image maps
made by the New Horizons spacecraft to gauge wind speed and direction. The
Hubble Space Telescope provided visible-light images of the storms, while the
Very Large Telescope in Chile used mid-infrared to glimpse the thermal
structure of the storms below the visible cloud tops.

The thermal heat images
showed that the Little Red Spot may already match the Great Red Spot for size,
although the latter still appears almost twice as large on the surface of
Jupiter?s atmosphere when examined in visible light.

"In the infrared, which
sees deeper beneath those clouds, the Little Red Spot appears to be part of an
interacting system that is actually larger than the Great Red Spot," Cheng
told SPACE.com.

The Little Red Spot has
steadily gained strength even as the Big Red Spot shrinks. Both storms have
winds that circulate in the opposite direction to that of a cyclone, or
counterclockwise, and appear "strikingly similar," Cheng said.

Seeing red

Astronomers remain mystified
by the angry red color of the storms. The Little Red Spot only changed color in
late 2005 after it formed from earlier mergers of three smaller storms.
Similarly, the newest third red spot began as an oval white storm.

These latest findings
support the theory that the most powerful storms dredge up material from below
Jupiter?s clouds and lift it into the upper atmosphere. That exposes the
material to solar ultraviolet radiation and causes the color change to red.

The newcomer storm may end
up merging with the Great Red Spot or getting pushed away when the two encounter
each other in August, assuming their paths remain the same. The Little Red Spot
lies at a lower latitude and will pass the Great Red Spot in June.

Such changes in Jupiter's
weather come as part of a global upheaval that began before the New
Horizons spacecraft visited last year. The idea that Jupiter is undergoing
global climate change was proposed in 2004 by Phil
Marcus, a mechanical engineer at the University of California, Berkeley. He predicted large changes in the southern hemisphere starting around 2006 that
would destabilize jet streams and spawn new storms.

Much of the activity in the
gas giant's South Equatorial Belt has disappeared and left the Great Red Spot
isolated, foreshadowing even greater changes to come.

"The Great Red Spot may
not always be the largest and strongest storm on Jupiter," said Glenn
Orton, planetary scientist and study coauthor at NASA's Jet Propulsion
Laboratory in Pasadena, Calif.